Innate Immune Anti-Inflammatory Response in Human Spontaneous Intracerebral Hemorrhage

Inhibition of Neutrophil Extracellular Traps: A Potential Therapeutic Strategy for Hemorrhagic Stroke

Stroke is a major health problem with high mortality and morbidity rates, partly due to limited treatment options. Inflammation has a critical role in the secondary damage that occurs following a stroke event. Neutrophil extracellular traps (NETs) are released by neutrophils and contribute to the progression of neuroinflammation that further worsens brain damage. The prevention of NET formation at sites of brain damage has been reported to prevent neuroinflammation and improve neurological deficits. The aim of this article was to assess the importance of NETs as a treatment target for hemorrhagic stroke in light of the available evidence. NETs are network structures that consist of decondensed DNA strands coated with granule proteins such as citrullinated histones, neutrophile esterase (NE), myeloperoxidase (MPO), and high mobility group protein B1 (HMGB1). Peptidyl arginine deiminase type-IV (PAD4) plays a key role in the formation of NETs. Inhibitors of NET formation, such as the PAD4-specific inhibitor GSK484, are effective at preventing inflammation and thus ultimately reducing brain damage after stroke. In conclusion, inhibition of NETs offers a potential therapeutic strategy for hemorrhagic stroke, although further research is needed to clarify the role of NETs in this condition.

Blood-brain barrier repair: potential and challenges of stem cells and exosomes in stroke treatment

Stroke is characterized with high morbidity, mortality and disability all over the world, and one of its core pathologies is blood-brain barrier (BBB) dysfunction. BBB plays a crucial physiological role in protecting brain tissues and maintaining homeostasis in central nervous system (CNS). BBB dysfunction serves as a key factor in the development of cerebral edema, inflammation, and further neurological damage in stroke patients. Currently, stem cells and their derived exosomes have shown remarkable potential in repairing the damaged BBB and improving neurological function after stroke. Stem cells repair the integrity of BBB through anti-inflammatory, antioxidant, angiogenesis and regulation of intercellular signaling mechanisms, while stem cell-derived exosomes, as natural nanocarriers, further enhance the therapeutic effect by carrying active substances such as proteins, RNAs and miRNAs. This review will present the latest research advances in stem cells and their exosomes in stroke treatment, as well as the challenges of cell source, transplantation timing, dosage, and route of administration in clinical application, aiming to discuss their mechanisms of repairing BBB integrity and potential for clinical application, and proposes future research directions. Stem cells and exosomes are expected to provide new strategies for early diagnosis and precise treatment of stroke, and promote breakthroughs in the field of stroke.

Potential blood biomarkers that can be used as prognosticators of spontaneous intracerebral hemorrhage: A systematic review and meta-analysis

BACKGROUND

Predicting nontraumatic spontaneous intracerebral hemorrhage (SICH) patient prognosis has been commonly practiced, particularly when providing informed consent and considering surgical treatment. Biomarkers might provide more real-time evaluation of SICH patients' condition than clinical prognostic scoring systems. This study aimed to evaluate the reliability of blood biomarkers in predicting prognosis in SICH patients by systematic review and meta-analysis.

METHODS

Studies that evaluated the association of blood biomarker(s) with mortality and/or functional outcome in SICH patients up to October 11, 2024, were identified through PubMed, Google Scholars, Scopus databases, and reference lists. Studies that satisfied the inclusion criteria were included in the meta-analyses. Good functional outcome was defined by patient's Glasgow Outcome Scale (GOS) ≥ 4 or modified Rankin scale mRS ≤ 2. Blood biomarkers were classified into the following categories: angiogenic factors, growth factors, inflammatory biomarkers, coagulation parameters, blood counts, and others. Individual meta-analysis was performed for every evaluation endpoint:7 days, 30 days, 3 months, 6 months, and 1 year. Meta-analyses were performed using Random Effect Mean-Difference with a 95% Confidence Interval for continuous data and visualized as forest plots in RevMan version 5.3 software. Cochrane Tool to Assess Risk of Bias in Cohort Studies was used to assess potential risk of bias of the included studies. GRADE Profiler was used to assess quality of evidence.

RESULTS

Seventy-seven studies fulfilled the inclusion criteria. Surviving SICH patients have significantly lower C-reactive protein (CRP), D-dimer, copeptin, S100β, white blood cell (WBC), monocyte, and glucose than non-surviving patients. SICH patients with good functional outcome have lower D-dimer, Interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), WBC count, neutrophil count, monocyte count, copeptin and significantly higher lymphocyte counts and calcium levels. Out of all blood biomarkers that were evaluated, only S100β and copeptin had very high effect size and high certainty of evidence.

CONCLUSION

It is interesting to notice that many blood biomarkers significantly associated with SICH patients' outcomes are related to inflammatory responses. This suggests that modulation of inflammation might be essential to improve SICH patients' prognosis. We confidently concluded that S100β and copeptin are the most reliable blood biomarkers that can be used as prognosticators in SICH patients. On other biomarkers, in addition to heterogeneities and inconsistencies, several factors might affect the conclusions of current meta-analysis; thus, future studies to increase the certainties of evidence and effect size on other biomarkers are crucial.

Mechanisms of hydrocephalus after intraventricular haemorrhage: a review

Intraventricular haemorrhage (IVH) is bleeding within the ventricular system, which in adults is usually mainly secondary to cerebral haemorrhage and subarachnoid haemorrhage. Hydrocephalus is one of the most common complications of intraventricular haemorrhage, which is characterised by an increase in intracranial pressure due to an increased accumulation of cerebrospinal fluid within the ventricular system, and is closely related to the patient's prognosis. Surgical methods such as shunt surgery have been used to treat secondary hydrocephalus in recent years and have been effective in improving the survival and prognosis of patients with hydrocephalus. However, complications such as shunt blockage and intracranial infection are often faced after surgery. Moreover, little is known about the mechanism of hydrocephalus secondary to intraventricular haemorrhage. This review discusses the mechanisms regarding the occurrence of secondary hydrocephalus after intraventricular haemorrhage in adults in terms of blood clot obstruction, altered cerebrospinal fluid dynamics, inflammation, and blood composition.

Intranasal Delivery of Curcumin Nanoparticles Improves Neuroinflammation and Neurological Deficits in Mice with Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) represents one of the most severe subtypes of stroke. Due to the complexity of the brain injury mechanisms following ICH, there are currently no effective treatments to significantly improve patient functional outcomes. Curcumin, as a potential therapeutic agent for ICH, is limited by its poor water solubility and oral bioavailability. In this study, mPEG-PCL is used to encapsulate curcumin, forming curcumin nanoparticles, and utilized the intranasal administration route to directly deliver curcumin nanoparticles from the nasal cavity to the brain. By inhibiting pro-inflammatory neuroinflammation of microglia following ICH in mice, reprogramming pro-inflammatory microglia toward an anti-inflammatory function, and consequently reducing neuronal inflammatory death and hematoma volume, this approach improved blood-brain barrier damage in ICH mice and promoted the recovery of neurological function post-stroke. This study offers a promising therapeutic strategy for ICH to mediate neuroinflammatory microenvironments.

Mesenchymal stem cell-loaded hydrogel to inhibit inflammatory reaction in surgical brain injury via mitochondria transfer

Neurosurgical procedures are the key therapeutic interventions for the cerebral hemorrhage and brain tumors. However, neurosurgical procedures inevitably cause surgical brain injury (SBI), which will induce hemorrhage and inflammation. Gelatin Sponges are still the primary hemostatic materials used in clinical, but their anti-inflammatory efficacy is poor. Herein, we developed a cross-linked gelatin hydrogel (GelMA) to load mesenchymal stem cells (MSC) and directly implant them to the SBI site. Upon contacting the SBI site, the GelMA showed better clotting performance than Gelatin Sponges. Moreover, the MSC can reduce oxidative stress and enhance mitochondrial fusion via mitochondria transfer, resulting in ameliorating mitochondrial damage and reducing inflammation. Thus, the GelMA containing MSC can effectively reduce brain edema and inflammation and improve neurological function in SBI mouse models. In addition, GelMA exhibits excellent hemocompatibility and low cytotoxicity. It also enhances the proliferation of MSCs and decelerates the rapid depletion of MSCs. Therefore, MSC-loaded GelMA exhibits excellent hemostatic and anti-inflammatory effects, making it a potential new-generation biomaterial for SBI.

Role of Neutrophils as Therapeutic Targets in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a major health problem. It is one of the most common types of stroke and results in mortality in approximately half of patients. More than half of the fatalities occur in the first 2 days. In addition to the mass effect after ICH hemorrhage, complex pathophysiological mechanisms such as intracranial vessel vasospasm, microthrombosis, and inflammatory immune reaction also increase brain damage. Both resident (including microglia and astrocytes) and circulating immune cells (including neutrophils, macrophages, and lymphocytes) involved in the inflammatory process. The inflammatory response is especially harmful in the acute phase due to harmful substances secreted by infiltrating immune cells. The inflammatory response also has beneficial effects, especially in the later stages. Their role in pathophysiology makes immune cells important therapeutic targets. General immunosuppressive approaches and depleting cell groups such as neutrophils or keeping them away from the lesion site may not be sufficient to prevent poor outcomes after ICH. This is most likely because they suppress anti-inflammatory activities and pro-inflammatory effects. Instead, directing immune cells to the beneficial subpopulation seems like a more rational solution. The pro-inflammatory N1 subpopulation of neutrophils damages the tissue surrounding ICH. In contrast, the N2 subpopulation is associated with anti-inflammatory reactions and tissue repair. Studies show that when neutrophils are polarized toward the N2 subpopulation, clinical outcomes improve and the volume of the infarct decreases. However, more research is still needed. This study aims to evaluate the role of neutrophils as immunotherapeutic targets in ICH in light of current knowledge.

Machine learning algorithms integrate bulk and single-cell RNA data to unveil oxidative stress following intracerebral hemorrhage

BACKGROUND

Increased oxidative stress (OS) activity following intracerebral hemorrhage (ICH) had significantly impacting patient prognosis. Identifying optimal genes associated with OS could enhance the understanding of OS after ICH.

METHODS

We employed single-cell RNA sequencing (scRNA-seq) to investigate the heterogeneity of OS across various cellular tiers following ICH, aiming to acquire biological insights into ICH. We utilized AUCell, Ucell, singscore, ssgsea, and AddModuleScore algorithms, along with correlation analysis, to identify hub genes influencing high OS post-ICH. Furthermore, we employed four machine learning algorithms, eXtreme Gradient Boosting, Boruta, Random Forest, and Least Absolute Shrinkage and Selection Operator, to identify the optimal feature genes. To validate the accuracy of our analysis, we conducted validation in ICH animal experiments.

RESULTS

After analyzing the scRNA-seq dataset using various algorithms, we found that OS activity exhibited heterogeneity across different cellular layers following ICH, with particularly heightened activity observed in monocytes. Further integration of bulk data and machine learning algorithms revealed that ANXA2 and COTL1 were closely associated with high OS after ICH. Our animal experiments demonstrated an increase in OS expression post-ICH. Additionally, the protein expression of ANXA2 and COTL1 was significantly elevated and co-localized with microglia. Pearson correlation coefficient analysis revealed a significant correlation between ANXA2 and OS, indicating strong consistency (r = 0.84, p < 0.05). Similar results were observed for COTL1 and OS (r = 0.69, p < 0.05).

CONCLUSIONS

Following ICH, ANXA2 and COTL1 might penetrate the brain via monocytes, localize within microglia, and enhance OS activity. This might help us better understand OS after ICH.

N6-Methyladenosine (m6A) Methylation Is Associated with the Immune Microenvironments in Acute Intracerebral Hemorrhage (ICH)

Researchers have recently found that N6-methyladenosine (m6A) is a type of internal posttranscriptional modification that is essential in mammalian mRNA. However, the features of m6A RNA methylation in acute intracerebral hemorrhage (ICH) remain unknown. To explore differential methylations and to discover their functions in acute ICH patients, we recruited three acute ICH patients, three healthy controls, and an additional three patients and healthy controls for validation. The m6A methylation levels in blood samples from the two groups were determined by ultrahigh-performance liquid chromatography coupled with triple quadruple mass spectrometry (UPLC-QQQ-MS). Methylated RNA immunoprecipitation sequencing (MeRIP-seq) was employed to identify differences in m6A modification, and the differentially expressed m6A-modified genes were confirmed by MeRIP-qPCR. We found no significant differences in the total m6A levels between the two groups but observed differential methylation peaks. Compared with the control group, the coding genes showing increased methylation following acute ICH were mostly involved in processes connected with osteoclast differentiation, the neurotrophin signaling pathway, and the spliceosome, whereas genes with reduced m6A modification levels after acute ICH were found to be involved in the B-cell and T-cell receptor signaling pathways. These results reveal that differentially m6A-modified genes may influence the immune microenvironments in acute ICH.

Mendelian randomization analysis identifies a genetic casual association between circulating C-reactive protein and intracerebral hemorrhage

BACKGROUND

The causal effect of C-reactive protein (CRP) on intracerebral hemorrhage (ICH) remains controversial. We discussed the causal association of CRP with ICH based on two-sample Mendelian randomization.

METHODS

The data from two genome-wide association studies (GWAS) of European ancestry was extracted, including circulating CRP levels (204,402 individuals) and ICH (1,687 cases and 201,146 controls). The inverse variance weighted (IVW) method was primary tool to evaluate the causal relationship of circulating CRP levels on ICH risk. MR-Egger regression and MR-PRESSO global test were utilized to identify pleiotropy. Heterogeneity was discussed with Cochran's Q test. The leave-one-out analysis explored the reliability of the results.

RESULTS

54 SNPs were identified as instrumental variables (IVs) for circulating CRP levels, and these IVs had no significant horizontal pleiotropy, heterogeneity, or bias. MR analysis demonstrated a causal relationship between elevated circulating CRP levels and decreased risk of ICH (ORIVW = 0.828, 95% CI 0.692-0.992, P = 0.040).

CONCLUSION

Elevated circulating CRP levels demonstrated a significant potentially protective causal relationship with risk of ICH.

Relationship between Uveitis and the Differential Reactivity of Retinal Microglia

Uveitis, a complicated group of ocular inflammatory diseases, can be affected by massive pathogenic contributors such as infection, autoimmunity, and genetics. Although it is well known that many pathological changes, including disorders of the immune system and disruption of the blood-retinal barrier, count much in the onset and progression of uveitis, there is a paucity of safe and effective treatments, which has exceedingly hindered the appropriate treatment of uveitis. As innate immune cells in the retina, microglia occupy a salient position in retinal homeostasis. Many studies have reported the activation of microglia in uveitis and the mitigation of uveitis by interfering with microglial reactivity, which strongly implicates microglia as a therapeutic target. However, it has been increasingly recognized that microglia are a nonhomogeneous population under different physiological and pathological conditions, which makes it essential to thoroughly have knowledge of their specific characteristics. The paper outlines the various properties of activated microglia in uveitis, summarizes the connections between their polarization patterns and the manifestations of uveitis, and ultimately is intended to enhance the understanding of microglial versatility and expedite the exploration of promising strategies for visual protection.

Cortical superficial siderosis is associated with reactive astrogliosis in cerebral amyloid angiopathy

BACKGROUND

Cortical superficial siderosis (cSS) has recently emerged as one of the most important predictors of symptomatic intracerebral hemorrhage and is a risk factor for post-stroke dementia in cerebral amyloid angiopathy (CAA). However, it remains unknown whether cSS is just a marker of severe CAA pathology or may itself contribute to intracerebral hemorrhage risk and cognitive decline. cSS is a chronic manifestation of convexal subarachnoid hemorrhage and is neuropathologically characterized by iron deposits in the superficial cortical layers. We hypothesized that these iron deposits lead to local neuroinflammation, a potentially contributory pathway towards secondary tissue injury.

METHODS

Accordingly, we assessed the distribution of inflammatory markers in relation to cortical iron deposits in post-mortem tissue from CAA cases. Serial sections from the frontal, parietal, temporal, and occipital lobes of nineteen autopsy cases with CAA were stained with Perls' Prussian blue (iron) and underwent immunohistochemistry against glial fibrillary acidic protein (GFAP, reactive astrocytes) and cluster of differentiation 68 (CD68, activated microglia/macrophages). Digitized sections were uploaded to the cloud-based Aiforia® platform, where deep-learning algorithms were utilized to detect tissue, iron deposits, and GFAP-positive and CD68-positive cells.

RESULTS

We observed a strong local relationship between cortical iron deposits and reactive astrocytes. Like cSS-related iron, reactive astrocytes were mainly found in the most superficial layers of the cortex. Although we observed iron within both astrocytes and activated microglia/macrophages on co-stains, there was no clear local relationship between the density of microglia/macrophages and the density of iron deposits.

CONCLUSION

Iron deposition resulting from cSS is associated with local reactive astrogliosis.

Role of Inflammatory Processes in Hemorrhagic Stroke

Hemorrhagic stroke is the deadliest form of stroke and includes the subtypes of intracerebral hemorrhage and subarachnoid hemorrhage. A common cause of hemorrhagic stroke in older individuals is cerebral amyloid angiopathy. Intracerebral hemorrhage and subarachnoid hemorrhage both lead to the rapid collection of blood in the central nervous system and generate inflammatory immune responses that involve both brain resident and infiltrating immune cells. These responses are complex and can contribute to both tissue recovery and tissue injury. Despite the interconnectedness of these major subtypes of hemorrhagic stroke, few reviews have discussed them collectively. The present review provides an update on inflammatory processes that occur in response to intracerebral hemorrhage and subarachnoid hemorrhage, and the role of inflammation in the pathophysiology of cerebral amyloid angiopathy-related hemorrhage. The goal is to highlight inflammatory processes that underlie disease pathology and recovery. We aim to discuss recent advances in our understanding of these conditions and identify gaps in knowledge with the potential to develop effective therapeutic strategies.

Exploring the pharmacological mechanism of Naoxueshu oral liquid in the treatment of intracerebral hemorrhage through weighted gene co-expression network analysis, network pharmacological and experimental validation

BACKGROUND

Intracerebral hemorrhage (ICH) is a life-threatening stroke subtype with high rates of disability and mortality. Naoxueshu oral liquid is a proprietary Chinese medicine that absorbs hematoma and exhibits neuroprotective effects in patients with ICH. However, the underlying mechanisms remain obscure.

PURPOSE

Exploring and elucidating the pharmacological mechanism of Naoxueshu oral liquid in the treatment of ICH.

STUDY DESIGN AND METHODS

The Gene Expression Omnibus (GEO) database was used to download the gene expression data on ICH. ICH-related hub modules were obtained by weighted gene co-expression network analysis (WGCNA) of differentially co-expressed genes (DEGs). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted using the obtained key modules to identify the ICH-related signaling pathways. Network pharmacology technology was applied to forecast the targets of Naoxueshu oral liquid and to establish a protein-protein interaction (PPI) network of overlapping targets between Naoxueshu oral liquid and ICH. Functional annotation and enrichment pathway analyses of the intersectional targets were performed using the omicsbean database. Finally, we verified the therapeutic role and mechanism of Naoxueshu oral liquid in ICH through molecular docking and experiments.

RESULTS

Through the WGCNA analysis, combined with network pharmacology, it was found that immune inflammation was closely related to the early pathological mechanism of ICH. Naoxueshu oral liquid suppressed the inflammatory response; hence, it could be a potential drug for ICH treatment. Molecular docking further confirmed that the effective components of Naoxueshu oral liquid docked well with CD163. Finally, the experimental results showed that Naoxueshu oral liquid treatment in the ICH rat model attenuated neurological deficits and neuronal injury, decreased hematoma volume, and promoted hematoma absorption. In addition, Naoxueshu oral liquid treatment also significantly increased the levels of Arg-1, CD163, Nrf2, and HO-1 around hematoma after ICH.

CONCLUSION

This study demonstrated that Naoxueshu oral liquid attenuated neurological deficits and accelerated hematoma absorption, possibly by suppressing inflammatory responses, which might be related to the regulation of Nrf2/CD163/HO-1 that interfered with the activation of M2 microglia, thus accelerating the clearance and decomposition of hemoglobin in the hematoma.

Activation of Nrf2 to Optimise Immune Responses to Intracerebral Haemorrhage

Haemorrhage into the brain parenchyma can be devastating. This manifests as spontaneous intracerebral haemorrhage (ICH) after head trauma, and in the context of vascular dementia. Randomised controlled trials have not reliably shown that haemostatic treatments aimed at limiting ICH haematoma expansion and surgical approaches to reducing haematoma volume are effective. Consequently, treatments to modulate the pathophysiological responses to ICH, which may cause secondary brain injury, are appealing. Following ICH, microglia and monocyte derived cells are recruited to the peri-haematomal environment where they phagocytose haematoma breakdown products and secrete inflammatory cytokines, which may trigger both protective and harmful responses. The transcription factor Nrf2, is activated by oxidative stress, is highly expressed by central nervous system microglia and macroglia. When active, Nrf2 induces a transcriptional programme characterised by increased expression of antioxidant, haem and heavy metal detoxification and proteostasis genes, as well as suppression of proinflammatory factors. Therefore, Nrf2 activation may facilitate adaptive-protective immune cell responses to ICH by boosting resistance to oxidative stress and heavy metal toxicity, whilst limiting harmful inflammatory signalling, which can contribute to further blood brain barrier dysfunction and cerebral oedema. In this review, we consider the responses of immune cells to ICH and how these might be modulated by Nrf2 activation. Finally, we propose potential therapeutic strategies to harness Nrf2 to improve the outcomes of patients with ICH.

Comprehensive analysis of immune-related biomarkers and pathways in intracerebral hemorrhage using weighted gene co-expression network analysis and competing endogenous ribonucleic acid

The immune response is an important part of secondary brain injury following intracerebral hemorrhage (ICH), and is related to neurological deficits and prognosis. The mechanisms underlying the immune response and inflammation are of great significance for brain injury and potential functional restoration; however, the immune-related biomarkers and competing endogenous ribonucleic acid (RNA) (ceRNA) networks in the peripheral blood of ICH patients have not yet been constructed. We collected the peripheral blood from ICH patients and controls to assess their ceRNA profiles using LCHuman ceRNA microarray, and to verify their expression with qRT-PCR. Two-hundred-eleven DElncRNAs and one-hundred-one DEmRNAs were detected in the ceRNA microarray of ICH patients. The results of functional enrichment analysis showed that the immune response was an important part of the pathological process of ICH. Twelve lncRNAs, ten miRNAs, and seven mRNAs were present in our constructed immune-related ceRNA network, combining weighted gene co-expression network analysis (WGCNA). Our study was the first to establish the network of the immune-related ceRNAs derived from WGCNA, and to identify leukemia inhibitory factor (LIF) and B cell lymphoma 2-like 13 (BCL2L13) as pivotal immune-related biomarkers in the peripheral blood of ICH patients, which are likely associated with PI3K-Akt, the MAPK signaling pathway, and oxidative phosphorylation. The MOXD2P-miR-211-3p -LIF and LINC00299-miR-198-BCL2L13 axes were indicated to participate in the immune regulatory mechanism of ICH. The goal of our study was to offer innovative insights into the underlying immune regulatory mechanism and to identify possible immune intervention targets for ICH.

Association between leukocyte subpopulations and hematoma expansion after spontaneous intracerebral hemorrhage: A retrospective cohort study

Aims

To verify the association between leukocyte subpopulations and hematoma expansion (HE) determined by two definitions in Chinese individuals who experienced spontaneous intracerebral hemorrhage.

Methods

We enrolled 471 patients. The 1/2ABC formula was used to gauge hematoma volume. The outcome was whether HE appeared within 72 h. We used Definition 1 (volume increase ≥6 mL or 33%) and Definition 2 (volume increase ≥12.5 mL or 33%) to define HE, respectively. Binary logistic regression analysis was used to assess the association between leukocyte subpopulations and HE. For statistically significant leukocyte subpopulations, we also performed subgroup analyses to assess differences between subgroups.

Results

Among 471 patients, 131 (27.81%) and 116 (24.63%) patients experienced HE based on Definition 1 and Definition 2, respectively. After adjusting for confounding factors, elevated monocyte count was associated with a higher risk of HE-Definition 1 [adjusted odds ratio (aOR) 2.45, 95% confidence interval (CI) 1.02–5.88, P = 0.0450] and HE-Definition 2 (aOR 2.54, 95% CI 1.04–6.20, P = 0.0399). Additionally, we compared the results before and after adjusting for coagulation parameters. Monocyte count was significantly correlated with HE only after adjusting for coagulation parameters. Increased neutrophil count was associated with a lower risk of HE-Definition 1 (aOR 0.91, 95% CI 0.84–1.00, P = 0.0463). No correlations were observed between lymphocyte and leukocyte counts and HE (P > 0.05), and no subgroup interactions were observed (interaction P > 0.05).

Conclusion

A higher monocyte count is associated with a higher HE risk regardless of the two definitions, after excluding the influence of the coagulation parameters, which facilitates risk stratification. Moreover, an increased neutrophil count is associated with a decreased risk of HE in the context of HE-Definition 1, which reflects the importance of standardizing the definition of HE.

Ventricular opening and cerebrospinal fluid circulation accelerate the biodegradation process of carmustine wafers suggesting their immunomodulation potential in the human brain

PURPOSE

Opening the ventricular system during glioblastoma surgery is often necessary, but the consequent effect on the tumor microenvironment of glioblastoma remains unknown. Implantation of carmustine wafer enables direct drug delivery to the tumor site; however, the exact mechanism of the wafer's biodegradation process is unclear, and the available data is limited to in vivo non-human mammalian studies. We hypothesized that the ventricular opening affects the degradation process of the wafer and the glioblastoma tumor microenvironment.

METHODS

This study included 30 glioblastoma patients. 21 patients underwent carmustine wafer implantation during initial surgery. All patients underwent repeated surgical resection upon recurrence, allowing for pathological comparison of changes associated with wafer implantation. Immunohistochemical analyses were performed using CD68, TMEM119, CD163, IBA1, BIN1, and CD31 antibodies to highlight microglia, macrophages, and tumor vascularity, and the quantitative scoring results were correlated with clinical, molecular, and surgical variables, including the effect of the ventricular opening.

RESULTS

The carmustine wafer implanted group presented significantly less TMEM119-positive microglia within the tumor (P = 0.0002). Simple and multiple regression analyses revealed that the decrease in TMEM119-positive microglia was correlated with longer intervals between surgeries and opened ventricular systems. No correlation was observed between age, methylated O6-methylguanine DNA methyltransferase promoter expression, and the extent of surgical resection.

CONCLUSIONS

Our study findings strongly suggest that biomaterials may possess immunomodulation capacity, which is significantly impacted by the ventricular opening procedure. Furthermore, our data highlights the pathophysiological effects of the ventricular opening within the surrounding human brain, especially after the wafer implantation.

Interactions between the Autonomic Nervous System and the Immune System after Stroke

Acute stroke is one of the leading causes of morbidity and mortality worldwide. Stroke-induced immune-inflammatory response occurs in the perilesion areas and the periphery. Although stroke-induced immunosuppression may alleviate brain injury, it hinders brain repair as the immune-inflammatory response plays a bidirectional role after acute stroke. Furthermore, suppression of the systemic immune-inflammatory response increases the risk of life-threatening systemic bacterial infections after acute stroke. Therefore, it is essential to explore the mechanisms that underlie the stroke-induced immune-inflammatory response. Autonomic nervous system (ANS) activation is critical for regulating the local and systemic immune-inflammatory responses and may influence the prognosis of acute stroke. We review the changes in the sympathetic and parasympathetic nervous systems and their influence on the immune-inflammatory response after stroke. Importantly, this article summarizes the mechanisms on how ANS regulates the immune-inflammatory response through neurotransmitters and their receptors in immunocytes and immune organs after stroke. To facilitate translational research, we also discuss the promising therapeutic approaches modulating the activation of the ANS or the immune-inflammatory response to promote neurologic recovery after stroke. © 2022 American Physiological Society. Compr Physiol 12:3665-3704, 2022.

Adiponectin Ameliorates GMH-Induced Brain Injury by Regulating Microglia M1/M2 Polarization Via AdipoR1/APPL1/AMPK/PPARγ Signaling Pathway in Neonatal Rats

Adiponectin (APN), a fat-derived plasma hormone, is a classic anti-inflammatory agent. Multiple studies have demonstrated the beneficial role of APN in acute brain injury, but the effect of APN in germinal matrix hemorrhage (GMH) is unclear, and the underlying molecular mechanisms remain largely undefined. In the current study, we used a GMH rat model with rh-APN treatment, and we observed that APN demonstrated a protective effect on neurological function and an inhibitory effect on neuroinflammation after GMH. To further explore the underlying mechanisms of these effects, we found that the expression of Adiponectin receptor 1 (AdipoR1) primarily colocalized with microglia and neurons in the brain. Moreover, AdiopR1, but not AdipoR2, was largely increased in GMH rats. Meanwhile, further investigation showed that APN treatment promoted AdipoR1/APPL1-mediated AMPK phosphorylation, further increased peroxisome proliferator-activated receptor gamma (PPARγ) expression, and induced microglial M2 polarization to reduce the neuroinflammation and enhance hematoma resolution in GMH rats. Importantly, either knockdown of AdipoR1, APPL1, or LKB1, or specific inhibition of AMPK/PPARγ signaling in microglia abrogated the protective effect of APN after GMH in rats. In all, we propose that APN works as a potential therapeutic agent to ameliorate the inflammatory response following GMH by enhancing the M2 polarization of microglia via AdipoR1/APPL1/AMPK/PPARγ signaling pathway, ultimately attenuating inflammatory brain injury induced by hemorrhage.

AQP2 Promotes Astrocyte Activation by Modulating the TLR4/NFκB-p65 Pathway Following Intracerebral Hemorrhage

Microglial and astrocyte activation and related cytokine secretion play key roles in secondary brain injury following intracerebral hemorrhage (ICH). We assessed the role of aquaporin (AQP)2 in immune response after ICH. We prospectively collected data from 33 patients with ICH and analyzed the serum AQP2 levels in these patients and age-matched healthy controls. A correlation analysis was also performed between patient serum AQP2 levels and clinical factors. In the rat ICH model, double-fluorescence staining for glial fibrillary acidic protein (GFAP) and AQP2 was performed to investigate the relationship between astrocytes and AQP2. Relative mRNA expression levels of GFAP and AQP2 were also measured. In the rat astrocyte cell line CTX-TNA2, toll-like receptor (TLR)4/nuclear factor kappa B (NFκB)-p65 pathway activation and GFAP levels were measured. The indirect influence of AQP2 on microglial polarization was assessed following exposure to the medium of astrocytes treated with AQP2-overexpression plasmid or silencing RNA. We found that the serum AQP2 expression was lower in patients with ICH. Sex and blood neutrophil count influenced serum AQP2 concentrations in patients with ICH on admission. Lower serum AQP2 levels were inversely correlated with 90-day Modified Rankin Scale scores after ICH, but were not correlated with National Institute of Health stroke scale (NIHSS) scores on admission. AQP2 overexpression and localization in GFAP-labeled astrocytes were observed in rats. AQP2 overexpression induced astrocyte activation with GFAP upregulation via TLR/NFκB-p65 signaling pathway activation in the rat astrocyte cell line CTX-TNA2. Astrocyte activation promoted interleukin-1β secretion. The medium of AQP2-overexpression astrocytes promoted the pro-inflammatory M1 phenotype in the immortal rat (HAPI) microglial cell line. Therefore, serum AQP2 is negatively correlated with post-ICH prognosis and may be a marker of inflammation in early-stage ICH. AQP2 overexpression promotes astrocyte activation and pro-inflammatory secretion, affects astrocyte-microglia crosstalk, and indirectly induces microglial polarization, which may augment inflammation after ICH.

Microglia and Astrocyte Function and Communication: What Do We Know in Humans?

Microglia and astrocytes play essential roles in the central nervous system contributing to many functions including homeostasis, immune response, blood-brain barrier maintenance and synaptic support. Evidence has emerged from experimental models of glial communication that microglia and astrocytes influence and coordinate each other and their effects on the brain environment. However, due to the difference in glial cells between humans and rodents, it is essential to confirm the relevance of these findings in human brains. Here, we aim to review the current knowledge on microglia-astrocyte crosstalk in humans, exploring novel methodological techniques used in health and disease conditions. This will include an in-depth look at cell culture and iPSCs, post-mortem studies, imaging and fluid biomarkers, genetics and transcriptomic data. In this review, we will discuss the advantages and limitations of these methods, highlighting the understanding these methods have brought the field on these cells communicative abilities, and the knowledge gaps that remain.

Serum Soluble Scavenger Receptor A Levels are Associated with Delayed Cerebral Ischemia and Poor Clinical Outcome After Aneurysmal Subarachnoid Hemorrhage: A Prospective Observational Study

OBJECTIVE

Scavenger receptor A (SRA), a pattern recognition molecule, is implicated in immune response after acute brain injury. We strived to identify serum soluble SRA (sSRA) as a potential biomarker of prognosis after aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

In this prospective observational study, we quantified serum sSRA levels of 131 aSAH patients and 131 healthy controls. A poor outcome was defined as extended Glasgow outcome scale (GOSE) scores of 1-4 at 90 days after injury. Relations of serum sSRA levels to severity, delayed cerebral ischemia (DCI) and poor outcome were assessed using multivariate analysis. Predictive efficiency was determined via area under receiver operating characteristic curve (AUC).

RESULTS

Serum sSRA levels were markedly higher in aSAH patients than in controls (median, 2.9 ng/mL versus 1.0 ng/mL; P < 0.001). Serum sSRA levels were independently correlated with Hunt-Hess scores (beta, 0.569; 95% confidence interval (CI), 0.244-0.894; P = 0.001), modified Fisher scores (beta, 0.664; 95% CI, 0.254-1.074; P = 0.002) and 90-day GOSE scores (beta, -0.275; 95% CI, -0.440-0.110; P = 0.005). Serum sSRA levels independently predicted DCI (odds ratio, 1.305; 95% CI, 1.012-1.687; P = 0.040) and a poor outcome (odds ratio, 2.444; 95% CI, 1.264-4.726; P = 0.008), as well as showed significant accuracy for the discrimination of DCI (AUC, 0.753; 95% CI, 0.649-0.857; P < 0.001) and a poor outcome (AUC, 0.800; 95% CI, 0.721-0.880; P < 0.001). Its combination with Hunt-Hess scores and modified Fisher scores displayed significantly improved AUCs for predicting DCI and poor outcome, as compared to any of them (all P < 0.05).

CONCLUSION

There is a significant elevation of serum sSRA levels after aSAH, which in close correlation with illness severity, are independently associated with DCI and poor clinical outcome after aSAH. Hypothetically, SRA may regulate immune response in acute brain injury after aSAH and serum sSRA is presumed to be a potential prognostic biomarker of aSAH.

Reduced M2 macrophages and adventitia collagen dampen the structural integrity of blood blister-like aneurysms and induce preoperative rerupture

Objective

Blood blister–like aneurysms (BBAs) are extremely rare aneurysms. They are predisposed to preoperative rerupture with a high case‐fatality rate. Here, we attempt to interrogate the distinct clinicopathology and the histological basis underlying its clinical rerupture.

Methods

Three middle meningeal arteries, 11 BBA (5 reruptured, 6 non‐rerupture) and 19 saccular aneurysm samples were obtained for histopathological investigation. Three reruptured BBAs, 3 non‐reruptured BBAs and 6 saccular (3 ruptured, 3 unruptured) aneurysms were obtained for quantitative flow cytometry analysis.

Results

Compared with true saccular aneurysms, the BBA aneurysm wall lacks arterial stroma cells including CD31+ endothelial cells and α‐SMA + smooth muscle cells. Only fibroblasts and adventitial collagen were observed in the BBA aneurysm wall. Meanwhile, BBAs were enriched with infiltrated inflammatory cells, especially polarized macrophages. Based on the rerupture status, those reruptured BBAs showed drastically reduced fibroblasts and adventitia collagen. Moreover, M2‐polarized macrophages were observed dominant in BBAs and exhibit repairing cellular functions based on their interplays with arterial fibroblasts. Reduced M2 macrophages and arterial tissue repairing modulation may be responsible for the decreasing collagen synthesis and fibrosis repairment, which potentially dampens the aneurysm integrity and induces BBA aneurysm reruputre.

Conclusions

BBAs poses histopathological features of occult pseudoaneurysms or dissecting aneurysms. Reduced M2 macrophages and adventitia collagen may dampen the structural integrity of BBAs and induce preoperative rerupture.

Microglia Phenotype and Intracerebral Hemorrhage: A Balance of Yin and Yang

Intracerebral hemorrhage (ICH) features extremely high rates of morbidity and mortality, with no specific and effective therapy. And local inflammation caused by the over-activated immune cells seriously damages the recovery of neurological function after ICH. Fortunately, immune intervention to microglia has provided new methods and ideas for ICH treatment. Microglia, as the resident immune cells in the brain, play vital roles in both tissue damage and repair processes after ICH. The perihematomal activated microglia not only arouse acute inflammatory responses, oxidative stress, excitotoxicity, and cytotoxicity to cause neuron death, but also show another phenotype that inhibit inflammation, clear hematoma and promote tissue regeneration. The proportion of microglia phenotypes determines the progression of brain tissue damage or repair after ICH. Therefore, microglia may be a promising and imperative therapeutic target for ICH. In this review, we discuss the dual functions of microglia in the brain after an ICH from immunological perspective, elaborate on the activation mechanism of perihematomal microglia, and summarize related therapeutic drugs researches.